Julie Tappero sees job prospects go up in marijuana smoke every day at the temporary staffing company she owns outside Seattle.

Since December 2012, when Washington state legalized recreational use of the drug, positive marijuana tests among West Sound Workforce's job applicants have more than tripled to about 15 percent. That means headaches for Tappero and many other companies struggling to maintain a drug-free workforce in drug-legal states.

These days, she has to bring in a larger pool of candidates and spend more time screening to rule out those who can't pass or won't take a drug test. She estimates that each of her four full-time recruiters is working an extra two hours a week filling jobs because of drug issues, most related to marijuana use.